This invention pertains to a process for high catalytic desulfurization of petroleum residua feedstocks to produce desulfurized hydrocarbon liquid products along with low net catalyst consumption. It pertains particularly to such process in which the hydrodesulfurization reaction is performed at higher temperature and lower pressure than normally used, along with high catalyst withdrawal and regeneration rate to minimize effective catalyst deactivation rate and increase catalyst age.
In catalyst desulfurization operations on petroleum residua feedstocks along with accompanying demetallization and denitrogenation reactions, use of high activity catalyst results in high deactivation rate for the catalyst due to carbon loading on the catalyst. A similar problem was recognized in U.S. Pat. No. 3,932,269 to Lehman, who disclosed a process for catalytic hydrocracking of petroleum residue feedstock using higher temperature and lower pressure than usual and using high catalyst replacement rates. But that process does not provide for a desired high level of desulfurization of the feedstock. Also, U.S. Pat. No. 3,893,911 to Rovesti, et al discloses a catalytic demetallization process for petroleum feedstock containing high metals content in which used catalyst is regenerated and returned to the reactor. However, a catalytic process for achieving high percentage desulfurization of petroleum residua with low consumption of fresh catalyst and increased catalyst age has evidently not previously been available.